A potential portal to other universes seems to have closed. The sharpest map yet made of light from the infant universe shows no evidence of "dark flow" – a stream of galaxy clusters rushing in the same direction that hinted at the existence of a multiverse.

That is the conclusion of 175 scientists working with data from the European Space Agency's Planck spacecraft. But champions of dark flow are not ready to give up yet, including one Planck scientist who says his team's analysis is flawed.